Skeletal muscle phenotype and blood pressure after acute exercises

The inter-individual responses in systolic blood pressure (SBP) vary from no change to marked reduction after acute exercise. We hypothesized that skeletal muscle phenotype modifies SBP responses.

Normotensive participants (12 males and 8 females, age 27 ± 6 years) performed two 30-min exercises, continuous and interval, by cycle ergometer on separate days. The area under the curve (AUC) for SBP was calculated until 60 min after exercise. Intensity of continuous exercise was 60% of peak exercise workload and interval exercise 8 × 1 min intervals (80-90% of peak exercise workload) with 2 min easy cycling between. The average workload was equal for both exercises (60%). Stroke volume (SV), cardiac output (CO), systemic vascular resistance (SVR), and baroreflex sensitivity (BRS) were measured at rest and after exercise. Muscle biopsies were taken from vastus lateralis on separate days, and the percentage of slow/fast fibers, capillary density and mitochondrial respiration were analyzed.

AUC for SBP was - 386 ± 387 vs -399 ± 228 mmHg·min (p = 0.89) after continuous and interval exercises, respectively. After interval exercise, AUC correlated with the percentage of fast fibers (r = - 0.60, p = 0.010) and, eg, with ΔCO (r = 0.45, p = 0.049) and ΔBRS (r = 0.48, p = 0.046). In the stepwise linear regression analysis, the percentage of fast fibers was the strongest predictor of AUC after interval exercise (partial correlation r = - 0.53, β = - 5.9, p = 0.024). AUC after continuous exercise did not correlate with any outcomes.

Participants with a greater proportion of fast fibers had superior SBP reductions after interval exercise. The muscle phenotype is an independent determinant of postexercise SBP after interval exercise.